Question

The diagram above shows a rectangular wire loop moving at a constant velocity in the direction of the red arrow into a uniform magnetic field. The magnetic field is represented by the blue dots
Which show that the magnetic field points out of the page.
As the loop continues to move into the magnetic field what happens in the wire loop?

• A. Conventional current flows around the wire loop in a clockwise direction and has a constant value.
• B. Conventional current flows around flows around the wire loop in a clockwise direction and increases in value as the loop moves further magnetic field.
• C. Conventional current flows around the wire loop in a counter clockwise direction and has a constant value.
• D. Conventional current flows around the wire loop in a counter-clockwise direction and increases in value as the loop moves further into the magnetic field.
• E. No current flows in the wire loop.

Answer 1

The correct option is A Conventional current flows around the wire loop in a clockwise direction and has a constant value.

We must understand Lenz's law and magnetic fields around current-carrying loops or coils to answer this question.

Lenz's law says that the current induced in a coil or loop of wire by a changing magnetic field or flux will always be in such a direction as to produce a magnetic field whose field or flux will oppose the change in magnetic field or flux that produced the current.

In this case, the flux through the loop is increasing out of the page. According to Lenz's law, the current in the loop will be in such a direction as to oppose this change in flux.

The flux the current in the loop produces must be into the page. We point the thumb of our right hand into the page to represent the direction of the magnetic field or flux produced by the current in the loop. Our fingers wrap in the direction of the conventional current induced around the loop, in this case, clockwise.

The current has a constant value, since the rate of change in flux is steady.

Remember–current is induced ONLY when there is a change in flux.

The correct answer is option "A".